The present invention relates to aircraft wings and wing tip devices, and more specifically, but not exclusively, to aircraft wings with moveable wing tip devices, actuation assemblies for use in such wings, aircraft incorporating such wings, and to methods of moving a wing tip device.
There is a trend towards increasingly large passenger aircraft, for which it is desirable to have correspondingly large wing spans. However, the maximum aircraft span is effectively limited by airport operating rules which govern various clearances required when manoeuvring around the airport (such as the span and/or ground clearance required for gate entry and safe taxiway usage).
Moveable wing tip devices have been suggested for use on passenger aircraft, where a wing tip device is movable between a flight configuration for use during flight, and a ground configuration for use during ground-based operations. In the ground configuration, the wing tip device is moved away from the flight configuration such that the span of the aircraft wing is reduced, thereby allowing use of existing gates and safe taxiway usage. By way of example, US 2013/0292508 discloses an arrangement in which the wing tip device is rotatable about a hinge located on the fixed (inner) wing. Other arrangements, such as that disclosed in WO2011/051699, enable a more complex movement of the wing tip device.
Aircraft having moveable wing tip devices, must be suitable for flight when the wing tip device is in the flight configuration yet must also be able to move the wing tip device, during ground-based operations. This can pose some difficulties:
Firstly, in the flight configuration it tends to be desirable to have a seal between the wing tip device and the fixed wing to ensure smooth airflow in this region and to minimise drag losses. However, if seals are used, they tend to be susceptible to significant wear during movement between the flight and the ground configurations.
Secondly, it is necessary for flight loads on the wing tip device to be adequately transferred into the main wing. Providing an arrangement in which the flight loads can be adequately transferred, whilst still enabling the wing tip device to be moved from that flight configuration to the ground configuration when required, can pose significant design difficulties.
There are also other technical challenges in providing a practical arrangement for moving a wing tip device between the flight and ground configurations. Amongst the issues to be addressed are: the problem of providing a safe and reliable arrangement to enable such movement without impacting unduly on the design of the wing; the problem of providing a compact and lightweight drive to effect the movement of the wing tip device; and the problem of how to secure the wing tip device in one or both of the flight and/or ground configurations.
The present invention seeks to mitigate at least some of the above-mentioned problems.